Recreating the Country blog |
'The interactions between plant roots and their symbiotic mycorrhizal fungi are quite intimate. Root exudates lure compatible fungal threads while deterring others that are not well-matched. The scientific literature is full of alluring words describing what comes next; entanglement, stimulus, penetration, intracellular exchange. The fungus ultimately forms an arbuscule (a tree-like structure) inside the plant root cells, specifically for the exchange of (nutrient-rich) fluids.' (A beautiful quote from mycologist Merlin Sheldrake, sourced through US organisation 'Real Organic'>) This week, after the soaking rains, I’ve noticed mushrooms and toadstools popping up in lawn areas in the town where I live. The exotic grass around these fungi is greener and at least 20% taller than the grass in nearby areas without fungi. This is a good example of a symbiotic relationship, where both the grass and the fungi are benefiting from growing together. The microbes associated with plants fall into five broad categories; the 'sexy' mycorrhizal fungi; the 'cocktail' of microbes that make up the microbiome of plants; nitrogen converting rhizobium bacteria; the 'harmful' parasitic fungi; and the 'soil building' saprophytic fungi.
This blog is about the microbes in categories 1,2 & 3, that are important to all living plants. Mycorrhizal fungi An estimated 90% of Australian plant species have a positive association with mycorrhizal fungi that live on the roots of plants. They combine in a very intimate relationship where both the plant and the fungi need each other to live well. There are usually several hundred species of mycorrhizal fungi in a few hectares of remnant herb-land, grassland, woodland, or forest. Walking through these remnant areas, you will have noticed the many colours and shapes of fungi pushing through the leaf litter. These are the fruiting bodies of various mycorrhizal fungi. Just as the fruit on a fruit tree is only a small part of the whole tree, what we see decorating the forest floor is just a small part of an immense network of root-like mycelium growing deep under the soil surface. These mycelia literally feed the tree with nutrients such as nitrogen, phosphorus and many of the minerals they need and in return plants feed the fungi with the starches and sugars it makes through photosynthesis. Since only 10% of mycorrhizal fungi produce fruiting bodies that pop up in natural places, most of the fungi that live in the soil are invisible to us. They are either too small to see or they form ‘fruit’ under the soil, known as truffles. Mycorrhizal fungi and the truffle ‘junkies’. Thousands of plants, ranging from tiny orchids to huge eucalyptus species, benefit from this symbiotic relationship with fungi. In a Western Australian study, 500 different species of mycorrhizal fungi were identified in small patches of remnant bush. In a healthy forest or woodland system, these beneficial fungi are spread around by the scratching and digging of small marsupials like Bettongs and Potoroos. These small kangaroos complement their diets by eating the fruit of fungi, particularly the truffles. It has been shown that forest and woodland plants are healthier and more diverse where these small fungi-eating marsupials still survive to enhance these ecosystems. Fungi loving marsupials will play an important role in keeping remnants and new biodiversity plantings healthy in the future. Once our most common kangaroos, they have become either threatened or extinct in most of mainland Australia. And yes, loss of their protected habitat at ground level has contributed to this crisis, but foxes and feral cats are their biggest threat. Boot camp for Burrowing Bettongs Protecting fungi spreading marsupials from predators like foxes and cats is a significant challenge that is generating some creative solutions. Predator-proof fencing has been around for decades, and it is very effective, though its high cost is often prohibitive. ($50,000/km in 2019) In the Sturt National Park, NSW, Ecologist Rebecca West is part of a team that has been training Burrowing Bettongs to avoid predators, and they’re getting results. Their most effective training method they refer to as ‘boot-camp for bettongs’. It sounds brutal to release a few feral cats into a 26 square kilometre fenced enclosure where the bettongs are living, but Rebecca and her team have found that they soon learn to avoid the cats. At first, the bettongs are naïve about the danger, but when they witness a bettong being killed and eaten, they quickly learn that cats are dangerous and that it’s smart to keep a safe distance. There is still a lot more to learn about designing the best boot camp for bettongs, but their initial trials are very encouraging. Discover more about Victoria's Eastern Bettongs in a charming story that brings you the facts in an entertaining way (7-minute read); Eastern Bettongs - 'truffle junkies or ecosystem engineers'. Plants have a microbiome. In the last decade, doctors have been emphasising the vital importance of the human microbiome to our health. These are the trillions of microscopic bacteria, viruses and fungi that live in our gut, on our skin, in our hair and in just about every part of the human body. In fact, more than half of the cells in our bodies are made up of these friendly, peace-loving, passengers that come along for the ride from the day we are born. Just as vital to plant health is their microbiome. Millions of microscopic bacteria and fungi live inside plants; their roots, stems, leaves, flowers and seed. These microbes are so important to a plant’s long-term health that they release specialised chemicals from their roots to invite them in. This cocktail of microbes is passed on to the next generation through a plant’s seed. So, a seed holds much more than the genetics of its parents, it also carries its parent’s microbiome. These specialist microbes are released when the seed germinates, and they enter its developing root system and start spreading throughout the plant. Dr Christine Jones, an expert in plant microbiology, puts it this way: “We now know that a seed has a core microbiome consisting of thousands of species of bacteria, archaea, fungi, and even some protists. The microbes in seeds are located inside the seed coat and surrounding the embryo. As the seed begins to germinate, they move into the radicle (primary root). Once the primary root has emerged, the first shoots appear. These too are colonised by microbes originating from the seed. As the plant grows, the core microbiome moves into the stems, leaves, flowers, fruits and eventually back into the seeds for the next generation." Remarkably, researchers have also shown that microbes from strong and healthy plants will move through the soil and into weaker neighbouring plants. They exchange their microbiome with other plants to help them through stressful times, however they’re quite fussy about which plants they help. They prefer to share their unique bacteria and fungi with plants from other plant families. Just as we benefit from living in human communities with wide-ranging skills and interests, plant communities that have evolved together as a diverse group benefit from this diversity. They try and maintain a variety of plant families in their communities by supporting struggling plants through tough times. Because of this constant sharing of fungi and bacteria, plants that live in a diverse plant community have more diverse microbiomes living in all of their plant parts. These richer microbiomes and the benefits that they provide are passed on to the next generation of plants in their seed. Christine Jones explains; “Microbes that begin in the seed are associated with plants through all stages of their growth and development. They are significant for nutrient acquisition and the production of plant-beneficial secondary metabolites that enhance tolerance to pests, disease and abiotic stresses such as contaminated soils or drought.” With revegetation works, Christine recommends including a minimum of 4 plant families to maximise the benefits of sharing and developing a more diverse microbiome. The flip side of this process is that plants from a depleted plant community will produce seeds with a depleted microbiome and a depleted ability to cope with stresses. Restoring the microbes The long-term survival of newly planted herb-lands, grasslands, woodlands, and forests will very likely depend on the presence of a collection of many types of mycorrhizal fungi and diverse plant microbiomes. Research in Western Australia and New South Wales has found that diverse fungal populations do not re-establish naturally in newly planted indigenous plantations. This is likely a reflection of the significant changes to soil chemistry after decades of grazing and cropping practices. The absence of the original mix of native plants has also depleted the soil of its associated mycorrhizae. The microbiomes in present-day native seed would also be depleted through the loss of so many important associations; plant to plant, plant to microbe, microbe to microbe. 'Though mycorrhizae are incredibly common (and functionally important) to land plants, they are in rapid decline. We are farming in ways that destroy these interactions, and we are now farming on half of the world’s land. Fertilizers, herbicides, and pesticides not only harm mycorrhizae, but they interfere with a plant's ability to form these relationships'. (Mycologist, Merlin Sheldrake) Creating links for soil microbes Creating links between patches of remnant bush by planting corridors of indigenous plants has the exciting potential to restore much of the lost mycorrhizal fungi. Remnants on roadsides and rivers and creeks, remnant patches on farms, small and large public reserves are all home to a diverse mix of an extraordinary variety of fungi and bacteria that once inhabited our entire Australian landscape. Planting a diverse mix of indigenous plants in an area that is linked to remnants, will modify the soil chemistry and microclimate through shade, wind shelter, the action and exudates from roots, the build-up of leaf litter, and the influence of the varieties of insects and birds that they attract. If we give the soil fungi avenues to spread, they are likely to use them, just as they have done for millennia, particularly when the soil environment begins to restore to its former character. Microorganisms have very effective airborne methods of spreading their spores and if we provide them with a suitable growing environment, they will surely adopt their new homes and flourish. An important part of change to soils will be the lowering of Nitrogen and Phosphorus to pre-European levels. Research has clearly shown that elevated soil Phosphorus suppresses mycorrhizal activity. Biostimulants. Biodynamic farmers inoculate their cropping and grazing paddocks with a dilute preparation called '500' which is made from aged cow manure. This is sprayed on cloudy days or at night to allow the microorganisms in the 500 to establish before sunshine makes contact with the soil and kills any microbes and spores that are still exposed. Organic growers inoculate seed with bio-stimulants sprayed onto dry seed before sowing. These can be made by diluting vermi-liquid to produce worm tea, or by soaking mature compost and adding water to make a compost tea. These liquids are rich in a diverse mix of microbes that benefit growing plants. Rhizobium bacteria. Another group of microorganisms that are important to plants are Rhizobium bacteria. These bacteria absorb atmospheric nitrogen and enable the legume plant families to absorb nitrogen through their roots. The families that directly benefit from this relationship include members of the Mimosaceae (e.g. wattles) and Caesalpiniaceae (e.g. cassias) and Fabaceae (e.g. davesia, dillwynia, indigophora, kennedia). The rhizobium bacteria live in nodules, which look like tiny potatoes, attached to the outside of the plant’s roots. Plants from these families can be successfully inoculated with rhizobium bacteria in the nursery before planting in the field. This is done by crushing nodules collected from seedling plants of the same species, (the nodules contain thousands of rhizobia) and adding the juice to water in a watering-can which is then watered over seedling trays when the seed is germinating. The rhizobia attach to the roots of the developing plants and support more vigorous growth when they are planted in soil. Other plant species growing nearby also benefit from the extra nitrogen that is added to the soil by these native legume plants. The microbial necromass - the largest land storage of carbon Deep under the soil, where oxygen is in short supply, there is an important though little known storage of carbon. In fact, it is where most organic soil carbon is stored more or less permanently. This makes it critically importance for carbon sequestration. It has been described as the largest store of carbon on land. At these deeper levels in the soil, it is efficiently recycled and contributes to the growth of the overall microbial biomass. It can provide up to 80% of the soil's organic matter. The microbial necromass is the accumulated remains of dead microbial cells and root cell fragments. It is permanent in the soil because the low levels of oxygen at deeper levels protect it from microbial decomposition. Necromass residues include dead microbe cells and their hyphae, fragments of cell walls plus the sugars, proteins, enzymes and DNA associated with microbial life. Land managers can increase soil carbon by optimizing necromass formation and by making it a critical component of efforts to minimise the effects of climate change. Sadly, they were toxic Yellow-stainers. I did get excited when I saw the enticing fairy-rings of mushrooms growing on roadside verges, but sadly it seems that good mushrooms are hard to find these days. On closer inspection, they turned out to be the toxic 'Yellow-stainers.’ Though it seems that the various exotic grasses growing with them didn’t find them toxic and actually benefit from being up close and cuddly. I'll take some solace though from knowing that the fresh lettuce and parsley that I put in my salad is full of the living microorganisms that make up the microbiomes of these plants. No doubt they will add diversity to my own flourishing gut flora and support my immunity in these covid times. To read more on fungi, how and where they grow, try the Australian National Botanic Gardens site. https://www.anbg.gov.au/fungi/what-is-fungus.html Also, the Interactive catalogue of Australian Fungi has some excellent photos. https://www.inaturalist.org/projects/fungimap-australia Current research into life in our soils -
You can be a citizen scientist and play a part, To care for our soils, we need to know more about them. While we know the life in our soils is in trouble, we need to know more. One important finding from the State of the Environment report was the need for more data on the biology of our soil to aid sustainable land use. Why? To date, most of our understanding of how farming impacts soil fungal diversity is based on overseas research. Despite the ecological importance of microbiota and their potential to accelerate sustainable food production, we still don’t have a clear picture of what mycorrhizal fungi live in Australia. To overcome this challenge, the Australian Research Council have launched 'Dig Up Dirt', a new nationwide research project designed to take stock of our beneficial soil fungi. Farmers, land managers and citizen scientists can send in soil samples so that Australia’s networks of soil fungi can be mapped. The data collected will also be fed into the international database - map fungi globally. This is a long-overdue step towards understanding soil fungi and conserving the life below our feet.
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Recapping the benefits of planting locals Indigenous plants are well adapted to the unique climate and soil of their local environment. The local insects, birds, and marsupials know and rely on the food and shelter that these very specialised plants provide. Imagine that a new supermarket chain has bought out your familiar corner store, and now it sells only brands you've never heard of and there's worse, the new supermarket only opens at inconvenient times. In the same way, local wildlife have evolved with the local plants and know their cycles, they know what the nectar/pollen tastes like and when it becomes available. They know where to find insects under the bark and which bark to use to build nests. Some wildlife may adapt quite well to the new plants in our gardens, but they may not be as healthy as they would be feeding on the indigenous plants that they have evolved with for millennia. Why plant wattles Wattles are important plants in most ecosystems because of the benefits they bring to other plants and to local wildlife. In nature, it’s common to see four or more wattle species in a wild ecosystem, ranging from the taller understorey plants down to the bushy shrub-layer wattles that I’d like to talk about today. Many of the shrub-sized wattles that are found in the Geelong region are rarely planted in gardens, yet they are a real asset in urban ecosystems. Not only are wattles an important source of food for wildlife, but they also add plant diversity, restore nitrogen to garden soils, add vibrant colour when they flower, and they’re quick growing, which makes a young garden look more grown-up. They are also quite long-living (15-20 years) and very competitive Planting small wattles under tall/mature trees The competitive nature of wattles is legendary. Many species of wattle evolved as pioneer plants that pave the way for other vegetation that needs shelter. They also compete well with existing trees. Two small bushy wattles that will fill in bare spaces and provide the very important shrub layer under mature trees are the delightful spring-flowering Gold-dust Wattle, A. acinaceae; which grows to 1 m tall, and the Myrtle Wattle, A. myrtifolia; with its distinctive red branching and red stems. It will reach a height of 2 meters. The Myrtle Wattle will brighten up the garden in mid-winter with its bright yellow pompom flower clusters. Getting plants started in dry areas under mature trees:
The benefits of providing a bushy habitat Their bushy form is very important if you want to attract small birds. If you want to bring Superb Fairy Wrens into your garden within the first few years of planting, include a tight clump of bushy wattles. For example, in the same space that you might plant a shrubby grevillea, plant three bushy wattles. Their interlocking branches will provide important protection from the neighbours’ cat that’s out prowling at night. If you want to provide super-safe accommodation for small birds, choose prickly wattles like the Hedge Wattle, A. paradoxa; or Prickly Moses, A. verticillata. The Hedge Wattle has superb bright yellow pompom flowers in spring that will brighten up any dark corner in the garden. Its extraordinary beauty is the paradox as it contrasts with the sharp cat-deterring spines along its branches and stems. A line of these shrubs planted 2 m apart will turn heads, and not just the fairy-wrens, when they’re in flower. I was interested to learn from Dr. John Morgan from Latrobe University that the common taller form of Hedge Wattle was introduced into Victoria from Kangaroo Island in the early 1900s to create stock-proof hedges. The form that is indigenous to Victoria is smaller (1-2 m) and less invasive. Prickly Moses is often found on waterways and will tolerate damper soil conditions than the Hedge Wattle. It can grow up to 4 m and its large pompom flowers from winter to spring are a refreshing pale yellow. The prickly part of this bush is its dark green leaves that taper to a point. Tough and sweet-smelling Some botanical names focus on an important feature of a plant that helps with its identification. For example, a beautiful shrubby wattle that is found throughout southern Victoria, as well as along the east coast, is the Sweet-scented Wattle, A. suaveolens which is the Latin word for sweet-smelling. This bushy sprawling wattle will grow to a height of 2 m and has delightful honey-scented creamy flower heads from June, continuing through the winter. It's one of the earliest wattles to flower. Like the smaller shrub wattles that compete well, the Sweet-scented Wattle will do the hard work under mature trees, fill up those empty spaces, and provide very useful wind shelter. Like all hardy plants that are planted in dry competitive environments, the Sweet-scented Wattle will need a little more effort to plant as described earlier, but the extra time spent will be well rewarded. Taller shrub wattles that will also perform well in these tough conditions are the Hop Wattle, A. stricta and the Varnish Wattle, A. verniciflua. Both will grow to around 3 m tall and both will provide robust shelter in windy, exposed positions. Both the Hop Wattle and the Varnish Wattle will also make a statement as single specimens in a small garden or as a natural-looking clump planted for wind shelter under mature trees. Both flower in spring, providing a welcome splash of refreshing yellow in the garden or plantation. The varnish wattle has particularly attractive small glossy leaves that give it a year-round appeal to gardeners. Food plants Two small bushy wattles that literally bring to the table something special are the Wirilda/Swamp Wattle, A retinodes; and the Coast Wattle, A. sophorae. Both are grown commercially for their edible seeds that are roasted and used for nutty food flavouring and a coffee additive. Click here to read about a commercial grower near Port Fairy. Both wattles will grow in tough garden environments and are well adapted to front-line coastal planting. Though, be cautious if you are planting A. sophorae because it is known for its 'weediness' along coastal fringes where it can spread and take over, smothering smaller indigenous plants. Both species display vivid yellow pompom flowers in spring. To make up the ten small wattles I have included a beautiful tough ground cover wattle from west of Geelong, The Thin-leaf Wattle, A. aculeatissima. This is an attractive, extremely hardy plant for rockeries or hot, exposed dry garden beds. This beautiful wattle will provide important shelter and a safe haven for skinks like the iconic Blue-tongue, as well as small birds. Its narrow leaves are a little prickly because of their pointed tip, which makes them an important habitat plant for all the small ground-living fauna that we want to attract to our gardens. Maintenance To keep small wattles looking fresh and attractive, chop them back every year or two after flowering, (or the following autumn if you plan to collect seed), with the hedge trimmers, by cutting the growing tips. This process of tip pruning not only makes the wattles bushier by increasing lateral growth, but also encourages them to flower more prolifically. Your clippings can be allowed to fall onto the garden bed as a woody mulch to suppress weeds. For prickly wattles, slide a tarpaulin under the plant before clipping to remove the thorny clippings that will make hand weeding unpleasant. These prickly clippings can be laid around tender shrubs to protect them from rabbits and hares. Avoid pruning wattles too hard, as it can cause them to die back. A rule of thumb is to avoid cutting stems that are larger than pencil thickness. Propagation Acacias are easily propagated from seed. To read more about this process and how to inoculate young plants to improve their health and vigour click here. Next month. Mycorrhizal fungi – the missing link in revegetation Acacia implexaAbout thirty years ago, I set off to collect my first Lightwood seed on a roadside near Lethbridge. I had been tipped-off by a local farmer, who said that it grew alongside a shrubby form of Blackwood. I remember driving up and down the gravel road several times, wondering if I had been sent on a wild goose chase. The trees on the roadside all looked like Blackwoods through my open window. At this stage of my nursery career, I had only read about Lightwood and didn’t know about the subtle features that distinguished it from it's very close relative, Blackwood. Though, a walk amongst the roadside trees soon revealed that there were indeed two different species growing side by side. With a more experienced eye, I can now comfortably identify Lightwoods while driving along a country road or highway, and it has become one of my favourite medium-sized wattles. Commonly pronounced – im-plex-a (no surprises there) Its species name, ‘implexa’ hints at another distinguishing feature of the tree. Its spiralling seed pods form tangled clumps and look very like untidy bird’s nests hanging from the branches. Implexus is Latin for tangled. Where does it grow? & what does it look like? The Lightwood is well suited to the soils and rainfall of the Geelong region. It can also be found growing on the basalt plains west of Geelong on stony barriers, in the eastern parts of Victoria, NSW and southern Queensland where the rainfall above 450 mm. In areas with high rainfall like the Otway Ranges, it’s unlikely to be seen, but this is where Blackwood’s excel and grow into forest giants. The Lightwood is an attractive, hardy, drought, frost-tolerant, upright small tree that grows 5-10 m tall. Though very like the Blackwood, its leaves are greener and distinctly sickle shaped. Another important difference between Lightwood and Blackwood is the seed. The glossy black seed of the Lightwood has a small bone coloured aril (the aril connects the seed to the pod) at the end of the seed, whereas the Blackwood has a large orange aril that surrounds the whole seed. The Lightwood has a rough bark and an attractive grey trunk. (click on the image to enlarge) The Lightwood is quite long-lived, thriving for 30 – 50 years. It still can be found on roadsides and on stony barriers, though it is becoming rarer. It’s more adaptable than the Blackwood and does well in dry, windy, exposed locations. The Lightwood is suited to all well drained soils. It's a fast-growing tree and will commonly reach two meters tall in the first twelve months after planting. The Lightwood is therefore very useful for erosion control, and its potential to sucker when its roots are disturbed is another benefit in eroded landscapes. Its tendency to sucker makes me cautious about recommending it for small gardens. Because it is a handsome tree, it is often planted as a street tree. An added benefit is its tolerance to pollution, and its shallow roots don’t raise footpaths. For a more detailed description of the leaves, flowers and seed pods, click to this Flora bank link Practical uses for the tree and its timber Its dense foliage makes it an ideal tree to plant for shelter on farms and as an understorey planting near remnant tall eucalypts like Yellow Gum and River Red Gum. Like all wattles, Lightwoods fix atmospheric nitrogen in the soil. This benefits all plants growing nearby. In Biorich plantations (designed for biodiversity and for income) it can be planted in clumps of 20 or more to allow for future maintenance and harvesting timber. Straight trees can be selected and ‘form-pruned’ to improve the future value of their harvested wood. ‘Form-pruning’ removes small branches from the main trunk, producing knot-free timber called clear-wood. Clear-wood is stronger and more valuable to furniture makers and wood turners because of its continuous, uninterrupted wood grain. Lightwood timber is hard, close-grained and dark brown with some pale stripes. The smaller branches and waste timber are also good firewood and are hot burning. Its lemon coloured pompom flowers in late summer provide good quality protein rich pollen for bees (crude protein is 23% - 27%). Traditional owner uses The very hard timber would have been useful for making Clapsticks and for carving small wooden bowls like the Coolamon. Traditional Owners boiled the bark of the Lightwood to produce a lotion that was applied to wounds to aid healing. This lotion could also relieve painful muscles and bruising. The leaves and bark are rich in soap forming chemicals called saponins. These produce a foam when crushed and mixed with water and were used to stun and catch fish. Nature notes The upright branching habit of the Lightwood provides excellent roosting sites for birds. Parrots and native pigeon’s eat the seed pods and seeds. Smaller birds like Silvereyes, feed on the many insects that are attracted to the late summer pollen rich flowers. Other insect eating birds like the Black-faced Cuckoo Shrike feed on grubs found under the bark. Like many wattle species, Lightwood is prone to attack from borers and gall forming wasps. The galls appear as brown, rounded woody growths on the branches. They can indicate that the tree is unhealthy (heavy clay soil or poor drainage can cause stress) or getting old. The galls can be cut off and burnt if they become unsightly. Propagation from seed The most convenient method to separate the acacia pods from the seed is to shake and rub the opened pods through a common garden sieve, a few handfuls at a time. Winnowing in a light breeze will remove the fine trash that passes through the sieve with the seed. After the Lightwood seeds are collected and cleaned. They can then be stored indefinitely in a jar or a zip lock plastic bag. Always record the date and place of collection. To germinate the seed, place the seed in a cup and pour boiled water over the seeds until they are well covered. Any seeds that float can be discarded because they are infertile. Allow the water to cool, pour off the water and pat the seeds dry. Sow in a shallow tray and cover the seed with potting mix. They should start to germinate within two weeks. Transplant into cells or forestry tubes when they are small and easy to handle. Add a pinch of slow release native plant fertiliser. Inoculating with rhizobia will increase the vigour and health of your trees when they are planted on in the field. Click here and scroll down for an easy acacia inoculation method. Grow plants on until they are about twice the height of the tube/cell and well hardened-off (toughened). |
Stephen Murphy is an author, an ecologist and a nurseryman. He has been a designer of natural landscapes for over 30 years. He loves the bush, supports Landcare and is a volunteer helping to conserve local reserves. |